Cross‐reactive LTP sensitization in food‐dependent exercise‐induced urticaria/anaphylaxis: a pilot study of a component‐resolved and in vitro depletion approach.

Background: Challenge tests for food‐dependent exercise‐induced anaphylaxis (FDEIA) carry some risk and have a high rate of false negatives. Our aim was to explore the usefulness of an in vitro immunodepletion assay and an allergen microarray test in the identification of IgE‐mediated cross‐reactive food allergens in patients with suspected FDEIA or food‐dependent exercise‐induced urticaria and panallergen sensitization. Methods: Three patients with a history of food dependent exercise induced urticaria/anaphylaxis and food panallergen sensitization in whom a food‐exercise challenge was not feasible were selected: a 25‐year‐old man with cholinergic urticaria who experienced generalized urticaria and angioedema during a soccer match after drinking a peach‐based soft drink; a 19‐year‐old woman with allergic rhinitis and controlled asthma who experienced anaphylactic shock while playing soccer, having eaten walnuts in the previous 90 min; and a 57‐year‐old man with baker's asthma who experienced four episodes of anaphylaxis during exercise after ingesting wheat‐containing food. All individuals underwent a diagnostic work‐up with skin prick tests, specific IgE (sIgE) and ImmunoCAP ISAC test. For the in vitro immunodepletion procedure, patients' serum was pre‐incubated with the suspected native allergen (peach, walnut, or wheat) in solid phase (ImmunoCAP). The eluted serum, containing unbound IgE, was collected and samples were re‐tested using Immunocap ISAC 112 and compared with baseline results. Results: All individuals were sensitized to lipid transfer proteins. The first patient was sensitized to Pru p 3, Cor a 8, Jug r 3, and Ara h 9; after pre‐incubation with peach there was 100% depletion of sIgE to all components. The second patient was sensitized to Pru p 3, Cor a 8, Jug r 3, and Ara h 9; immunodepletion with walnut depleted sIgE to Ara h 9 by 67%, Pru p 3 and Pla a 3 (60%), Art v 3 (75%), Jug r 3 (88%), and Cor a 8 (100%). The third patient was sensitized to Pru p 3, Jug r 3, Ara h 9, and Tri a 14; immunodepletion with wheat depleted Tri a 14 only (100%). Conclusions: In vitro immunodepletion might be a useful diagnostic tool in food dependent exercise induced urticaria/anaphylaxis with panallergen sensitization, particularly for identifying the culprit allergen and guiding dietary elimination recommendations. [ABSTRACT FROM AUTHOR]